In products (parts) such as various household electrical appliances and construction members including decoration parts related to automobiles, various decorations such as a wood tone, a cloth tone and a metal tone have been used in order to enhance design property, but recently, a metal tone appearance of high luminance has been demanded.
As a procedure of imparting a metal tone to various molded parts, the most generally used procedure is coating. While coating can impart various designs or functions to products, organic solvents or the like are used frequently, and it greatly influences on the environment. In addition, recycling cannot be easily performed in some cases by the influence of a coating film, and the presence of a coating step is regarded as a problem under a current rise in an environmental problem.
As another procedure of imparting a metal tone, there are plating and deposition. Also in the case of plating and deposition, there is a problem of difficulty in recycling due to a metal layer, but particularly in the case of plating, since the influence on the environment due to a heavy metal is great, a substitute for the heavy metal has been strongly demanded. Further, in the case of plating and deposition, since electromagnetic shielding property is generated due to the metal layer, when used as a material for decorating automobiles and cellular phones, radio disturbance is generated in some cases, which has been becoming a problem.
As a material having a metal-like luster without using a metal, conventionally, there has been an example (see, for example, Patent Literatures 1 to 2) of using a film which selectively reflects the light of a particular wavelength, by alternately laminating resin layers having different refraction indices into a multilayer. However, in these techniques, since a difference in refraction indices of resins used is too great, affinity between the resin layers is insufficient, and there is a defect of generating inter-layer peeling, and therefore it is actually difficult to use the material in molding decoration. In addition, there is also a problem that, when a film having a low reflection ratio such as a half-mirror is produced, coloring is generated.
In response to these problems, there is a film of a metal luster tone without coloring, which is realized by adequately adjusting a difference in refraction indices of resins used to suppress inter-layer peeling and, at the same time, forming an especial layer structure (see Patent Literature 3). In this case, when a film having a low reflection ratio such as a half-mirror is produced, there is a problem that the film is slightly easily colored, and an interference pattern is easily seen. In addition, since the distribution in a layer thickness is greatly different between a front side and a back side, there is a problem that, when the film is prepared into a molding, warping or the like is generated due to a difference in thermal shrinkage/thermal expansion property between the front side and the back side.
In addition, there is a problem that, when a multilayer laminated film such as one in Patent Literatures 1 to 3 is insert-molded, a defective molding phenomenon called washout (hereinafter, referred to as WashOut in some cases) occurs. WashOut is a phenomenon in which a film or ink around a gate portion is melted and flown. Particularly, in the case of a multilayer laminated film, there is a problem that, even when the film is not melted, bending deformation in a portion of a layer shifts an interference reflection wavelength, and particular discoloration is generated, which becomes a defect.
[Patent Literature 1] JP-A-Hei03-41401
[Patent Literature 2] JP-A-Hei04-295804
[Patent Literature 3] WO 2007/20861 Pamphlet